Heated fluid flow continues to be crucial in achieving improved performance and efficiency in a broad range of mechanical, pharmaceutical, industrial processes and medical applications. In the pharmaceutical industry, for example, when a fluid having a solvent is blended with other active elements, accurate temperature control over the fluid is important for achieving quality drugs. A heater is not permitted to make direct contact with fluid because of pharmaceutical manufacturing processes. Similarly, in food and brewery process industries, temperature control is also necessary.
Furthermore, in medical applications, heated fluid flow is often used as a carrier of medicine to bring the medical element into a patient's body. Hemodialysis and peritoneal dialysis are two typical medical applications that require a heated fluid to be delivered to a patient. Peritoneal dialysis is an example of a medical application which requires the heating of the fluid. It can be appreciated, of course, that the use of peritoneal dialysis is not limited in this application.
Peritoneal dialysis is a method for removing waste, such as urea and potassium from the blood, as well as excess fluid, when the kidneys are incapable of this (i.e. in renal failure). The recent dialysis process employing peritoneal dialysis has been attracting attention because the cost of treatment is less expensive than with the dialysis process employing an artificial kidney and peritoneal adhesion can be prevented.
A peritoneal dialysis apparatus typically includes a fluid infusing bag connected to a fluid container (bag) containing a peritoneal fluid to be infused or delivered to a patient's peritonean (peritoneal cavity) and a reservoir bag connected to a drained fluid container (bag) for recovering the fluid drained from the patient. A pressure chamber, which accommodates the fluid infusing bag and reservoir bag, is formed in the housing of a dialysis apparatus or peritoneal dialysis apparatus. When the pressure in the pressure chamber is increased or decreased, the fluid infusing bag or reservoir bag pumps. The apparatus housing typically found in the art has a heater for heating the fluid in the fluid infusing bag held by the housing to a temperature within a predetermined temperature range.
Peritoneal dialysis is a form of renal dialysis, and is thus a renal replacement therapy. Because a patient's body can only adopt the fluid with a tight temperature range that is similar to that of a human body, the fluid must be heated prior to infusion to the abdominal cavity of a patient.
One example of a peritoneal dialysis machine is disclosed in U.S. Pat. No. 5,989,423, entitled “Disposable cassette, delivery set and system for peritoneal dialysis” which issued to Kamen et al. on Nov. 23, 1999 and is incorporated herein by reference. Such a device includes a disposable cassette for use in peritoneal dialysis that includes a pair of diaphragms, tube connectors, pump chambers, channel paths, and valves. In the configuration of U.S. Pat. No. 5,989,423, a disposable dialysate delivery set is provided for use in peritoneal dialysis and includes a cassette, multiple liquid flow paths, multiple valves, tube connectors, and disposable flexible plastic tubes to convey dialysate to and from the patient and other locations within the system. A system is also described for performing peritoneal dialysis includes disposable supply containers of fresh dialysate, a cassette including a pump, a disposable heater container, and conduits for carrying fresh dialysate and carrying heated dialysate.
The fluid of peritoneal dialysis is generally glucose or other contents dissolved in water with common strengths of around 0.5%, 1.5%, 2.5% and 4.25% respectively. Relying on gravity, the fluid from a fluid bag, such as bag 11 depicted in FIG. 1 is flowed to a disposable cassette, in which different active contents are mixed at a reservoir. The cassette is placed in a cassette machine 10 depicted in FIG. 1, and a pump within the machine 10 places pulsed pressure at the diaphragm side of the reservoir to push the fluid through the outlet of the cassette to the patient.
The cassette machine 10 shown in FIG. 1 is a prior art device for heating a fluid. Device 10 includes the use of a bag 11 containing fluid. The bag 11 is placed on a pan 13. The pan 13 is heated by a flexible heater (not shown) located on the back side of the pan 13. Thus, the whole bag 11 of fluid is heated before the fluid flows into a disposable cassette (not shown) located within a dialysis machine. Such an approach presents a straightforward solution for heating the fluid; however, it has its drawbacks.
First, the heating system including the pan is quite bulky especially for applications at patients' home. Second, this type of approach is less efficiency because it has to heat up all the fluid in the bag rather than the portion of the fluid that will go to the abdomen of patient directly. Thus, the system approach depicted in FIG. 1 requires a long warm-up time, high electrical power and a large heating system to maintain the temperature of the whole bag of fluid. Third, in such an approach, it is difficult to accurately control the temperature of fluid infused into the abdomen of the patient due to a long path of the heated fluid delivered from the bag to the patient, which may cause the temperature of the heated fluid out of the range requested.
Given those disadvantages, it is believed that several solutions can be developed to overcome the aforementioned issues associated conventional heating methods.